The growth kinetics of discontinuous precipitation in an Al-18.6%Zn containing 0, 0.04, 0.09Ge was studied at 150, 200?? by optical microscopy, X-ray, TEM and resistometric technique.
The amount of continuous precipitation and total degree of decomposition was quantified by using resistometric work. The amount of continuous precipitation increased with increasing Ge within aging time 1 minute. With increasing Ge, the decomposition rate decreased. The amount of continuous precipitation was least at 0.01Ge and increased with increasing Ge rather than Al-Zn binary alloy on the apparant onset of discontinuous precipitation.
With increasing the amount of continuous precipitation of the apparent onset of discontinuous precipitation, the initiation of discontinuous precipitation is fast. After discontinuous precipitation started, With increasing the amount of continuous precipitation, the available chemical free energy decreased and cell growth rate increased, but the strain energy associated with the G.P zone increased. It is believed that the strain energy associated with G.P zone plays a major role on moving the cell boundary. : The kinetics of discontinuous precipitaion was influenced by the kinetics of continuous precipitaion.
